migration/dirtyrate: skip sampling ramblock with size below MIN_RAMBLOCK_SIZE

In order to sample real RAM, skip ramblock with size below MIN_RAMBLOCK_SIZE
which is set as 128M.

Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
Reviewed-by: David Edmondson <david.edmondson@oracle.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Li Qiang <liq3ea@gmail.com>
Message-Id: <1600237327-33618-9-git-send-email-zhengchuan@huawei.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

2 files changed, 26 insertions, 0 deletions

diff --git a/migration/dirtyrate.c b/migration/dirtyrate.c
index 0f78aa3af7..ee47e2bc27 100644
--- a/migration/dirtyrate.c
+++ b/migration/dirtyrate.c
@@ -138,6 +138,18 @@ static void get_ramblock_dirty_info(RAMBlock *block,
     strcpy(info->idstr, qemu_ram_get_idstr(block));
 }
 
+static bool skip_sample_ramblock(RAMBlock *block)
+{
+    /*
+     * Sample only blocks larger than MIN_RAMBLOCK_SIZE.
+     */
+    if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
+        return true;
+    }
+
+    return false;
+}
+
 static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
                                       struct DirtyRateConfig config,
                                       int *block_count)
@@ -150,6 +162,9 @@ static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
     bool ret = false;
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
+        if (skip_sample_ramblock(block)) {
+            continue;
+        }
         total_count++;
     }
 
@@ -159,6 +174,9 @@ static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
     }
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
+        if (skip_sample_ramblock(block)) {
+            continue;
+        }
         if (index >= total_count) {
             break;
         }
@@ -225,6 +243,9 @@ static bool compare_page_hash_info(struct RamblockDirtyInfo *info,
     RAMBlock *block = NULL;
 
     RAMBLOCK_FOREACH_MIGRATABLE(block) {
+        if (skip_sample_ramblock(block)) {
+            continue;
+        }
         block_dinfo = find_block_matched(block, block_count, info);
         if (block_dinfo == NULL) {
             continue;
diff --git a/migration/dirtyrate.h b/migration/dirtyrate.h
index 312debca6f..be5b8ec2b1 100644
--- a/migration/dirtyrate.h
+++ b/migration/dirtyrate.h
@@ -24,6 +24,11 @@
  */
 #define RAMBLOCK_INFO_MAX_LEN                     256
 
+/*
+ * Minimum RAMBlock size to sample, in megabytes.
+ */
+#define MIN_RAMBLOCK_SIZE                         128
+
 struct DirtyRateConfig {
     uint64_t sample_pages_per_gigabytes; /* sample pages per GB */
     int64_t sample_period_seconds; /* time duration between two sampling */